News: Research Highlights

Tue January 1, 2013

Quantum Logic between Remote Quantum Registers

We considered two approaches to dark-spin-mediated quantum computing in hybrid solid-state spin architectures. First, we reviewed the notion of eigenmode-mediated unpolarized spin-chain state transfer and extended the analysis to various experimentally relevant imperfections: quenched disorder, dynamical decoherence, and uncompensated long-range coupling. In finite-length chains, the interplay between disorder-induced localization and decoherence yielded a natural optimal...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Dissipative Preparation of Spin Squeezed Atomic Ensembles in a Steady State

We presented and analyzed an approach for the generation of atomic spin-squeezed states. Our method involved the collective coupling of an atomic ensemble to a decaying mode of an open optical cavity. We demonstrated the existence of a collective atomic dark state, decoupled from the radiation field. Through the explicit construction of that state we...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Attractive Photons in a Quantum Nonlinear Medium

In this paper, we demonstrate for the first time a bound state of two photons. We illuminate a dense and cold atomic ensemble with weak laser light underconditions of electromagnetically induced transparency to an atomic Rydberg state. When we detune the control laser coupling the unstable intermediate state to the Rydberg level, the probe photons...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Single-photon Nonlinearities in Two-mode Optomechanics

We presented a detailed theoretical analysis of a weakly driven, multimode optomechanical system, in which two optical modes were strongly and near-resonantly coupled to a single mechanical mode via a three-wave mixing interaction. We calculated one- and two-time intensity correlations of the two optical fields and compared them to analogous correlations in atom-cavity systems. Nonclassical...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Keldysh Approach for Non-equilibrium Phase Transitions in Quantum Optics: Beyond the Dicke Model in Optical Cavities

We investigated nonequilibrium phase transitions for driven atomic ensembles interacting with a cavity mode and coupled to a Markovian dissipative bath. In the thermodynamic limit and at low frequencies, we showed that the distribution function of the photonic mode was thermal, with an effective temperature set by the atom-photon interaction strength. That behavior characterized the...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Heisenberg-limited Atom Clocks based on Entangled Qubits

We presented a quantum-enhanced atomic clock protocol based on groups of sequentially larger Greenberger-Horne-Zeilinger (GHZ) states, which achieved the best clock stability allowed by quantum theory up to a logarithmic correction. The simultaneous interrogation of the laser phase with such a cascade of GHZ states realized an incoherent version of the phase estimation algorithm that...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Stretchable Photonic Crystal Cavity with Wide Frequency Tunability

We reported a new approach for the realization of a flexible photonic crystal (PC) cavity that enabled wide-range tuning of its resonance frequency. Our PC cavity consisted of a regular array of silicon nanowires embedded in a polydimethylsiloxane (PDMS) matrix and exhibited a cavity resonance in the telecommunication band that could be reversibly tuned over...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Probing Real-space and Time Resolved Correlation Functions with Many-body Ramsey Interferometry

We proposed to use Ramsey interferometry and single-site addressability, available in synthetic matter such as cold atoms or trapped ions, to measure real-space and time-resolved spin correlation functions. Those correlation functions directly probed the excitations of the system, which made it possible to characterize the underlying many-body states. Moreover, they contained valuable information about phase...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Non-Equilibrium Fractional Quantum Hall State of Light

We investigated the quantum dynamics of systems, which involved small numbers of strongly interacting photons. Specifically, we developed an efficient method to investigate such systems when they were externally driven with a coherent field. Furthermore, we showed how to quantify the many-body quantum state of light via correlation functions. Finally, we applied that method to...
Read More »
News type:
Research Highlights
Tue January 1, 2013

Enhanced Anti-ferromagnetic Exchange between Magnetic Impurities in a Superconducting Host

It is generally believed that superconductivity only weakly affects the indirect exchange between magnetic impurities. If the distance r between impurities is smaller than the superconducting coherence length (), this exchange is thought to be dominated by RKKY interactions, identical to those in a normal metallic host. This perception is based on a perturbative treatment...
Read More »
News type:
Research Highlights